Composition for conversion into cellulose derivatives and process of preparing same



Patented Jan. 29, 1929.

'UNE'EED STATES I W 6 earner OFF-ICE.

GEORGE A. RICHTER, BERLIN, NEW HAMPSHIRE, ASSIGNOR TO BROWN OOMPAN Y, OF BERLIN, NEW HAMIJESHIIKEE, A CORPORATION OF MAINE.

COMPOSITION r03 couvnasron m'ro cELLuLosn DERIVATIVES AND raoonss or ranranme SAME.

No Drawing,

that process, a raw or unbleached pulp, pretreated if desired with an oxidizing or chlorinating reagent, is treated with caustic soda solution of mercerizing strength to effect a solution and removal of non-alpha cellulose constituent therefrom and accordingly a refinement ofsuch pulp to'a high alpha cellulose content. Such pulp, when bleached,

a constitutes an excellent material for the preparation of cellulose derivatives such as Xanthate and nitrocellulose. Also, in application, Serial No. 140,67 7 filed October 9, 1926, the advantages of mercerizing wood pulp, but more particularly a bleached high alpha cellulose wood pulp, prior to conversion into such derivatives as the nitrocellulose, are disclosed. In suchlatter case, mercerization of the pulp in'bulk form, particularly in the results in a product which when nitrated and dissolved in a suitable solvent yields solutions of lower viscosity and of markedlv better color than those prepared from nitrated,

unmercerized pulp. 4 w

The present invention has for its object to decrease the acid retention and increase the nitrocellulose yield when pulp is mercerized in bulk form rather than in thin paper or tissue form, and then nitrated, as upon nitration the acid retention of such bulk pulp is appreciably higher and the yield appreci'ably lower than when unmercerize pulp is made into tissue which is mercerized and. then nitrated as described in application,

Serial No. 140,675, filed October 9, 1926, by Milton Q. Schur and Royal H. Rasch. The quality of the nitrocellulose obtained from mercerized bulk pulp and the physical and 4 chemical characteristics of films, lacquers, or

other products prepared from such nitrocel-' lulose are apparently as goodas when similar pulp in tissue form is nitrated. The higher acid retention and lower yield are believed to be attributable to the higher absorptivity of mercerized fiberin bulk form over that in paper form.. Thus, owing to the higher retention of acid by the bulk fiber, a greater loss of the fiber apparently takes place during presence of a small quantity of an oxidant,

Application filed Match 3, 1927. Serial No. 172,568.

nitration and when after centrifugingit is submergpd in water,'mytheory being-that the was water effects a slower dilution and washing out of the acid in the bulk fiber than when tissue is washed, and that during such slower dilution, acid concentrations are produced in the bulk fiber which favor a hydrolysis of nitrocellulose. i

If, however, it be attempted to'form paper or tissue from the mercerized fiber prior to nitration, difliculty is experienced, as mercerized fiber is unhydratable, and even after long beating, if such beaten fiber is run off on a papermaking machine, a loose, bulky paper of non-uniform thickness results, which upon nitration yields practically no improvement over bulk pulp. Even if the mercerized pulp be beaten many times as long as is usually necessary for unmercerized pulp, the paper formed therefrom is altogether too loose and bulky to improve nitration results.

I have found that if mercerized .pulp, and more particularly'mercerized alpha pulp, is uniformly mixed with unmercerized beaten or unbeaten pulp, the composite. pulp may be formed into a tissue or light weight paper which yields materially improved results upon nitration. For instance, the mercerized pulp may be uniformly mixed with a relatively small proportion of, well-beaten, unmercerized pulp, as in a-hollander. Or the mercerized pulp may be uniformly mixed with unbeaten, unmercerized pulp and then beaten until suflicient hydration of the unmercerized'pulp has been effected to. bond" the mercerized pulp together into a wellfelted tissue. Preferably, however, the firstrnentioned procedure of uniformly mixing a well-beaten pulp with the mercerized pulp is,

practised, in orderto conserve power and to preserve the length of-mercerized fiber, as

ability for nitration.

In producing tissue such as herein desired,

the following mode of procedure has been found to give proper results. Sulphite fiber,

- same fiber or from different fiber.

alpha fiber, cotton fiber, or the like, is treated in shredded or bulk condition with a caustic soda solution of mercerizing strength. The treatment may, for instance, be carried out by the treating process and in the apparatus disclosed and claimed in my application, Serial No. 128,398, filed August 10, 1926, for example. A small quantity of an oxidant, such as sodium hypochloritc, may be added to the solution, particularly when an unbleached or partially bleached fiber is being mercerized, as the oxidant reacts with and removes coloring matter from the pulp. Sulphite fiber is preferably mercerized in an unbleached or only partially bleached condition, as described in my application, Serial N 0. 77,624, filed Dec. 24, 1925, for if bleached sulphite pulp is mercerized, an appreciable loss and degradation of its alpha cellulose content takes place. The mercerized sulphite fiber may then be bleached to the desired whiteness. After mercerization, about 5700f an over-beatenhigh alpha cellulose-containing fiber is uniformly disseminated throughout the mercerized fiber, as by circulation or beating for a while in a hollander or other beater. Or 5% to of unbeaten, unmercerized fiber may be added to the mercerized fiber, and the mixture then beaten until the desired hydration of the unmercerized fiber has been effected. The composite fiber is run off on a paper machine into thin paper or tissue suitable for nitration. Such tissue is well-felted and relatively dense, so that nitration results in appreciable improvement in both acid retention and yield.

The composition of mercerized, and beaten, unmercerized fiber may be produced from the For instance, the mercerized fiber may be mercerized sulphite fiber, and unmercerized, beaten fiber may be alpha Wood fiber or cotton fiber, alone or in admixture or'both the mercerized fiber and beaten, unmercerized fiber may be produced from a high grade sulphite fiber. While for best results the composition ismade .into tissue, nevertheless such a composition of mercerized fiber and beaten, unmercerized fiber, when nitrated 1n bulk form, gives improved results over a composition of mercerized fiber alone. Thus, the composition of the present invention may be flufi'ed mechanically to resemble cotton linters, or maybe formed on a cylinder machine or Fourdrinier Wire from a very dilute suspension of pulp into a relatively thick, porous sheet, and dried on the mold or wire, either with or Without squeezing, and nitrated in such form.

The great utility of the process herein described is that the advantages of mercerizing fiber in bulk form prior to nitration, as well as the advantages arising from a desirable physical condition of fiber when nitration is being effected, are both realized. In plant practice, it is more economical to mercerize and'zwash pulp in large quantities in bulk form and to recover the mercerizing solution, rather than to mercerize a sheet or tissue. By the process of the present invention, economical advantages. of mercerizing fiber in .bulkform are enjoyed, and at the same time a tissue of good nitrating characteristics may be manufactured therefrom. Having thus described my invention, it is obvious that it is subject to change and modification without departing from its s )irit or scope as set forth in the appended claims.

\Vhat I claim is:

1. A cellulose fiber composition comprising a mixture of mercerized and unmercerized fiber.

2. A cellulose fiber composition comprising a mixture of mercerized fiber and beaten, unmercerized fiber. 1

3. A cellulose fiber composition comprising a substantially. homogeneous mixture of a preponderant proportion of mercerized fiber and a subordinate proportion of beaten, unmercerized fiber. 1

4. A paper comprising mercerized and unmercerizcd cellulose fiber.

5. A paper comprising mercerized cellulose fiber uniformly interfelted with beat-en, unmercerized cellulose fiber.

6. A process step which comprises running off on a paper machine a mixture of mercerized and unmercerized cellulose fiber.

7. A process which comprises-running off on a paper machine a substantially uniform mixture of mercerized and unmercerized cellulose fiber and calendering the paper.

8. A process which comprises uniformly mixing mercerized and unmercerized cellulose fiber, and running the mixture OH on a paper machine.

- 9. A process which comprisesuniformly mixing mercerized cellulose fiber and unmercerized, beaten cellulose fiber, and running the mixture off on a paper machine.

10. A process which comprises running off on a paper machine a mixture of mercerized and unmercerized cellulose fiber, and converth ative.

11. A process which comprises running off on a paper machine a substantially uniform mlxture of mercerized cellulose fiber and ing the resulting paper into a cellulose deriv beaten, umnercerized cellulose fiber, and nitrating the resulting paper.

12. A process which comprises uniformly mixing mercerized cellulose fiber and unmer-' cerized, beaten cellulose fiber, running the mixture off on a paper; machine, and nitrating the resulting paper.

In testimony whereof I have affixed my signature.

GEORGE A. RICHTER. 

